Dyed photoresists and methods and articles of manufacture comprising same

ABSTRACT

The present invention provides new photoresist compositions that comprise a resin binder, a photoactive component, particularly an acid generator, and a dye material that contains one or more chromophores that can reduce undesired reflections of exposure radiation. Preferred dye compounds are polymeric materials that include one or more chromophores such as anthracene and other polycyclic moieties that effectively absorb deep UV exposure radiation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to new photoresist compositions particularlysuitable for deep U.V. exposure and having the capability of forminghighly resolved features of submicron dimension.

2. Background Art

Photoresists are photosensitive films for transfer of images to asubstrate. They form negative or positive images. After coating aphotoresist on a substrate, the coating is exposed through a patternedphotomask to a source of activating energy such as ultraviolet light toform a latent image in the photoresist coating. The photomask has areasopaque and transparent to activating radiation that define a desiredimage to be transferred to the underlying substrate. A relief image isprovided by development of the latent image pattern in the resistcoating. The use of photoresists is generally described, for example, byDeforest, Photoresist Materials and Processes, McGraw Hill Book Company,New York (1975), and by Moreau, Semiconductor Lithography, Principals,Practices and Materials, Plenum Press, New York (1988).

More recently, certain “chemically amplified” photoresist compositionshave been reported. Such photoresists may be negative-acting orpositive-acting and rely on many crosslinking events (in the case of anegative-acting resist) or deprotection reactions (in the case of apositive-acting resist) per unit of photogenerated acid. In other words,the photogenerated acid acts catalytically. In the case of the positivechemically amplified resists, certain cationic photoinitiators have beenused to induce cleavage of certain “blocking” groups pendant from aphotoresist binder, or cleavage of certain groups that comprise aphotoresist binder backbone. See, for example, U.S. Pat. Nos. 5,075,199;4,968,581; 4,883,740; 4,810,613; and 4,491,628, and Canadian PatentApplication 2,001,384. Upon selective cleavage of the blocking groupthrough exposure of a coating layer of such a resist, a polar functionalgroup is provided, e.g., carboxyl or imide, which results in differentsolubility characteristics in exposed and unexposed areas of the resistcoating layer.

An important property of a photoresist is image resolution. A developedphotoresist image of fine line definition, including lines of sub-micronand sub-half micron dimensions and having vertical or essentiallyvertical sidewalls is highly desirable to permit accurate transfer ofcircuit patterns to an underlying substrate.

However, many current photoresists are not capable of providing suchhighly resolved fine line images.

For example, reflection of activating radiation used to expose aphotoresist often poses limits on resolution of the image patterned inthe photoresist layer. Reflection of radiation from thesubstrate/photoresist interface can produce variations in the radiationintensity in the photoresist during exposure, resulting in non-uniformphotoresist linewidth upon development. Radiation also can scatter fromthe substrate/photoresist interface into regions of the photoresistwhere exposure is not intended, again resulting in linewidth variations.The amount of scattering and reflection will typically vary from regionto region, resulting in further linewidth non-uniformity.

Reflection of activating radiation also contributes to what is known inthe art as the “standing wave effect”. To eliminate the effects ofchromatic aberration in exposure equipment lenses, monochromatic orquasi-monochromatic radiation is commonly used in photoresist projectiontechniques. Due to radiation reflection at the photoresist/substrateinterface, however, constructive and destructive interference isparticularly significant when monochromatic or quasi-monochromaticradiation is used for photoresist exposure. In such cases the reflectedlight interferes with the incident light to form standing waves withinthe photoresist. In the case of highly reflective substrate regions, theproblem is exacerbated since large amplitude standing waves create thinlayers of underexposed photoresist at the wave minima. The underexposedlayers can prevent complete photoresist development causing edge acuityproblems in the photoresist profile. The time required to expose thephotoresist is generally an increasing function of photoresist thicknessbecause of the increased total amount of radiation required to expose anincreased amount of photoresist. However, because of the standing waveeffect, the time of exposure also includes a harmonic component whichvaries between successive maximum and minimum values within thephotoresist thickness. If the photoresist thickness is non-uniform, theproblem becomes more severe, resulting in variable linewidth control.

Variations in substrate topography also give rise to resolution-limitingreflection problems. Any image on a substrate can cause impingingradiation to scatter or reflect in various uncontrolled directions,affecting the uniformity of photoresist development. As substratetopography becomes more complex with efforts to design more complexcircuits, the effects of reflected radiation become more critical Forexample, metal interconnects used on many microelectronic substrates areparticularly problematic due to their topography and regions of highreflectivity.

With recent trends towards high-density semiconductor devices, there isa movement in the industry to shorten the wavelength of exposure sourcesto deep ultraviolet (DUV) light (300 nm or less in wavelength) includingexcimer laser light (248.4 nm), ArF excimer laser light (193 nm),electron beams and soft x-rays. The use of shortened wavelengths oflight for imaging a photoresist coating has resulted in greaterpenetration of the photoresist layer and increased reflection of theexposing energy back into the photoresist layer. Thus, the use of theshorter wavelengths has exacerbated the problems of reflection from asubstrate surface.

It thus would be desirable to have new photoresist compositions thatcould provide highly resolved fine line images, including images ofsub-micron and sub-half micron dimensions. It would be further desirableto have such new photoresist compositions that could be imaged with deepU.V. radiation. It would be particularly desirable to have suchphotoresists that reduced reflections of exposure radiation.

SUMMARY OF THE INVENTION

The present invention provides new photoresist compositions that ingeneral comprise a resin binder, a photoactive component, particularlyan acid generator, and a dye material that contains one or morechromophores that can reduce undesired reflections of exposureradiation. Preferred dye compounds are polymeric materials (generallyreferred to herein as “resin dyes”) that include one or morechromophores that effectively absorb deep UV exposure radiation.

Preferred chromophores of the dyes of the invention are carbocyclic orheterocyclic polycyclic moieties. Anthracene is a particularly preferredchromophore, including anthracene esters such as groups of the formula—(C═O)O(CH₂)_(n)anthracene, wherein n is an integer from 0 to about 6.Other suitable chromophores include quinolinyl and ring-substitutedquinolinyl derivatives such as hydroxyquinolinyl, phenanthrenyl andacridine groups.

Generally, about 5 to 90 percent of the units of a resin dye of theinvention comprises such chromophores, more preferably about 10 to 80percent of the resin dye units. Generally, resin dyes of the inventionwill have a weight average molecular weight of at least about 500daltons. Preferred resin dyes of the invention have an optical densityof at least about 4 units/μ at 248 nm. Copolymer resin dyes aregenerally preferred, including anthracene copolymers, particularlyanthracene/acrylic resins.

It has been found that use of a dye resin of the invention in aphotoresist imparts significant lithographic improvements to the resist,including substantial reductions of undesired reflections of exposureradiation and enhanced resolution and masking linearity of developedresist images. See the results of the examples which follow.

The invention further provides methods for forming a relief image andnovel articles of manufacture comprising substrates such as amicroelectronic wafer or a flat panel display substrate coated withphotoresist composition of the invention. Novel polymers are alsoprovided. Other aspects of the invention are disclosed infra.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, preferred dye compounds of photoresists of theinvention include one or more chromophores that can effectively absorbdeep UV radiation to prevent or at least significantly reduce undesiredreflections of the exposure radiation.

Aromatic groups, particularly polycyclic hydrocarbon or heterocyclicunits, are typically preferred deep UV chromophores of the dyecompounds, e.g. groups having from two to three or more fused orseparate rings with about 3 to 8 ring members in each ring and zero tothree N, O or S atoms per ring. Such chromophores include substitutedand unsubstituted anthracenyl, substituted and unsubstitutedphenanthryl, substituted and unsubstituted acridine, substituted andunsubstituted quinolinyl and ring-substituted quinolinyls such ashydroxyquinolinyl groups.

As discussed above, substituted or unsubstituted anthracenyl groups areparticularly preferred chromophores. For example, preferred resin dyeshave pendant anthracenyl groups, particularly acrylic resins of thefollowing Formula I:

wherein each R is independently substituted or unsubstituted alkylpreferably having about 10 carbon atoms, more typically 1 to about 6carbons;

W is a bond or substituted or unsubstituted alkylene preferably having 1to about 4 carbons, and preferably is substituted or unsubstitutedmethylene (—CH₂—);

each R¹ may be independently halogen (F, Cl, Br, I); substituted orunsubstituted alkyl preferably having 1 to about 12 carbon atoms;substituted or unsubstituted alkoxy preferably having 1 to about 12carbon atoms; substituted or unsubstituted alkenyl preferably having 2to about 12 carbon atoms; substituted or unsubstituted alkynylpreferably having 2 to about 12 carbon atoms; substituted orunsubstituted alkylthio preferably having 1 to about 12 carbon atoms;cyano; nitro; amino; hydroxyl; etc.;

m is an integer of from 0 (where the anthracenyl ring is fullyhydrogen-substituted) to 9, and preferably m is 0, 1 or 2;

x is the mole fraction or percent of alkyl acrylate units in the polymerand preferably is from about 10 to about 80 percent;

y is the mole fraction or percent of anthracene units in the polymer andpreferably is from about 5 to 90 percent; and

each Z is a bridge group between polymer units, e.g. substituted orunsubstituted alkylene preferably having 1 to about 10 carbon atoms,more typically 1 to about 6 carbon atoms, or more preferably 1 to about3 carbons and optionally substituted by alkyl having 1 to about 3carbons, or Z is substituted or unsubstituted alkenyl or alkynyl,preferably having 2 to about 10 carbons and optionally substituted byalkyl having 1 to about 3 carbons. The polymer also may contain otherunits if desired, but preferably the polymer will contain at least about10 mole percent of anthracene units. Hydroxyalkyl is a particularlypreferred R group, especially alkyl having a primary hydroxy group suchas where R is 2-hydroxyethylene (—CH₂CH₂OH). Preferably the resin bindercontains 9-(methylene)anthracene ester units (i.e. where W is methylenesubstituted at the 9-position of the pendant anthracene). A specificallypreferred resin dye comprises the structure of Formula III shown inExample 1 which follows.

Other preferred resin dyes of the invention comprise substituted orunsubstituted quinolinyl or a quinolinyl derivative that has one or moreN, O or S ring atoms such as a hydroxyquinolinyl. The polymer maycontain other units such as carboxy and/or alkyl ester units pendantfrom the polymer backbone. A particularly preferred resin dye is anacrylic polymer of the following Formula II:

each R² is independently substituted or unsubstituted alkyl preferablyhaving 1 to about 10 carbon atoms, more typically 1 to about 6 carbons;

W′ is a bond or substituted or unsubstituted alkylene preferably having1 to about 4 carbons, and preferably is a bond;

G is a carbon, nitrogen, oxygen or sulfur;

each R³ may be independently halogen (F, Cl, Br, I); substituted orunsubstituted alkyl preferably having 1 to about 12 carbon atoms;substituted or unsubstituted alkoxy preferably having 1 to about 12carbon atoms; substituted or unsubstituted alkenyl preferably having 2to about 12 carbon atoms; substituted or unsubstituted alkynylpreferably having 2 to about 12 carbon atoms; substituted orunsubstituted alkylthio preferably having 1 to about 12 carbon atoms;cyano; nitro; amino; hydroxyl; etc.;

m is an integer of from 0 (where the ring is fully hydrogen-substituted)to 7, and preferably m is 0, 1 or 2.

x′ is the mole fraction or percent of alkyl acrylate units in thepolymer and preferably is from 10 to about 80 percent;

y′ is the mole fraction or percent of quinolinyl or hydroxyquinolinylunits in the polymer and preferably is from about 5 to about 90 percent;and

each Z is a bridge group between polymer units, e.g. substituted orunsubstituted alkylene preferably having 1 to about 10 carbon atoms,more typically 1 to about 6 carbon atoms, or more preferably 1 to about3 carbons and optionally substituted by alkyl having 1 to about 3carbons, or Z is substituted or unsubstituted alkenyl or alkynyl,preferably having 2 to about 10 carbons and optionally substituted byalkyl having 1 to about 3 carbons. The polymer also may contain otherunits if desired, but preferably the polymer will contain at least about10 mole percent of quinolinyl and/or hydroxyquinolinyl units.Hydroxyalkyl is a particularly preferred R² group, especially alkylhaving a primary hydroxy group such as where R² is 2-hydroxyethylene.

The above-mentioned substituted groups (including substituted groups R,R¹, R², R³, Z, W, W′ and substituted chromophores) may be substituted atone or more available positions by one or more suitable groups such ase.g. halogen (particularly F, Cl and Br); cyano; hydroxyl, nitro,alkanoyl such as a C₁₋₆ alkanoyl group such as acyl and the like; alkylgroups having from 1 to about 8 carbon atoms; alkenyl and alkynyl groupshaving one or more unsaturated linkages and 2 to about 8 carbon atoms;alkoxy groups having from 1 to about 6 carbons; etc.

Resin dyes of the invention are preferably synthesized by polymerizingtwo or more different monomers where at least one of the monomersincludes a chromophore group, e.g. an anthracenyl, quinolinyl orhydroxyquinolinyl group. A free radical polymerization is suitablyemployed, e.g., by reaction of a plurality of monomers to provide thevarious units in the presence of a radical initiator preferably under aninert atmosphere (e.g., N₂ or argon) and at elevated temperatures suchas about 70° C. or greater, although reaction temperatures may varydepending on the reactivity of the particular reagents employed and theboiling point of the reaction solvent (if a solvent is employed). Seethe examples which follow for exemplary reaction conditions. Suitablereaction temperatures for any particular system can be readilydetermined empirically by those skilled in the art based on the presentdisclosure. A reaction solvent may be employed if desired. Suitablesolvents include alcohols such as propanols and butanols and aromaticsolvents such as benzene, chlorobenzene, toluene and xylene.Dimethylsulfoxide, dimethylformamide and THF are also suitable. Thepolymerization reaction also may be run neat. A variety of free radicalinitiators may be employed to prepare the copolymers of the invention.For example, azo compounds may be employed such asazobis-2,2′-isobutyronitrile (AIBN) and 1,1′-azobis(cyclohexanecarbonitrile). Peroxides, peresters, peracids andpersulfates also can be employed.

Also, while less preferred, a preformed resin may be functionalized withchromophore units to provide the dye. For example, a phenolic resin suchas a novolac or poly(vinylphenol) polymer or copolymer can be reactedwith an anthranyl carboxylic acid.

Preferably the resin dyes of the invention will have a weight averagemolecular weight (Mw) of about 500 to about 10,000,000 daltons, moretypically about 1,000 to about 1,000,000 daltons, even more typically anMw of about 5,000 to 200,000 daltons, still more typically about 5,000to about 110,000 daltons and a molecular number molecular weight (Mn) ofabout 500 to about 1,000,000 daltons. Particularly preferred are resindyes having an Mw of at least about 7,000 or 8,000 daltons, andpreferably an Mw of less than about 80,000 daltons. Molecular weights(either Mw or Mn) of the polymers of the invention are suitablydetermined by gel permeation chromatography.

Resin dyes preferably exhibit good absorbance at deep UV wavelengthssuch as within the range of from 100 to about 300 nm. More specifically,preferred resin binders of the invention have optical densities of atleast about 3 absorbance units per micron (Absorb. units/μ) at about 248nm, preferably from about 5 to 20 or more absorbance units per micron at248 nm, more preferably from about 8 to 20 or more absorbance units permicron at 248 nm. Higher absorbance values for a particular resin can beobtained by increasing the percentage of chromophore units on the resin.As used herein, optical density of a resin is determined by thefollowing procedure: spin cast a solution of the resin onto a siliconwafer (e.g. 4 inch wafer) and then a polished quartz wafer (e.g. 4 inchwafer). Wafers are soft baked for 60 seconds at approximately 110° C.Coating layer thickness are determined using a Prometrix SM300 ThicknesMeasurement tool. Absorbance spectral curves are generated for thecoating layers, e.g. using a Cary 13 UV-VIS Spectrophotometer.Absorbances are normalized for a 1.0 μm thick film.

The concentration of a resin dye within a photoresist composition mayvary within relatively broad ranges, and in general the resin dye isemployed in a concentration of from about 10 to 70 weight percent of thetotal of the dry components of a photoresist, more typically from about20 to 50 weight percent of the total dry components (all resistcomponents except solvent carrier).

As discussed above, in addition to dye compound, photoresists of theinvention contain resin binder and photoactive components. Negativeresists of the invention also include a crosslinking component. Thephotoactive component may suitably be either a photoacid or a photobasegenerator, although photoacid generators may be more typically employed,particularly for positive-acting resists.

Preferably the photoresist resin binder has functional groups thatimpart alkaline aqueous developability to the photoimaged resistcomposition. Preferred are resin binders that comprise polar functionalgroups such as hydroxyl or carboxylate and the resin binder is used in aresist composition in an amount sufficient to render the resistdevelopable with an aqueous alkaline solution.

Generally preferred resist resin binders are phenolic resins includingphenol aldehyde condensates known in the art as novolak resins, homo andcopolymers or alkenyl phenols and homo and copolymers ofN-hydroxyphenyl-maleimides.

Examples of suitable phenols for condensation with a aldehyde,especially formaldehyde, for the formation of novolak resins includephenol; m-cresol; o-cresol; p-cresol; 2,4-xylenol; 2,5-xylenol;3,4-xylenol; 3,5-xylenol; thymol and mixtures thereof. An acid catalyzedcondensation reaction results in formation of a suitable novolak resinwhich may vary in molecular weight (Mw) from about 500 to 100,000daltons. Poly(vinylphenols) may be prepared, e.g., as disclosed in U.S.Pat. No. 4,439,516. Preferred resin binders and the preparation thereofare also disclosed in U.S. Pat. No. 5,128,230.

Poly(vinylphenols) may be formed by block polymerization, emulsionpolymerization or solution polymerization of the corresponding monomersin the presence of a catalyst. Vinylphenols useful for the production ofpolyvinyl phenol resins may be prepared, for example, by hydrolysis ofcommercially available coumarin or substituted coumarin, followed bydecarboxylation of the resulting hydroxy cinnamic acids. Usefulvinylphenols also may be prepared by dehydration of the correspondinghydroxy alkyl phenols or by decarboxylation of hydroxy cinnamic acidsresulting from the reaction of substituted or nonsubstitutedhydroxybenzaldehydes with malonic acid. Preferred polyvinylphenol resinsprepared from such vinylphenols have a molecular weight (Mw) range offrom about 2,000 to about 60,000 daltons.

Copolymers containing phenol and nonaromatic cyclic alcohol units alsoare preferred resin binders for resists of the invention and may besuitably prepared by partial hydrogenation of a novolak orpoly(vinylphenol) resin. Such copolymers and the use thereof inphotoresist compositions are disclosed in U.S. Pat. No. 5,128,232 toThackeray et al.

Further preferred resin binders include resins formed frombishydroxymethylated compounds, and block novolak resins. See U.S. Pat.Nos. 5,130,410 and 5,128,230 where such resins and use of same inphotoresist compositions is disclosed. Additionally, two or more resinbinders of similar or different compositions can be blended or combinedtogether to give additive control of lithographic properties of aphotoresist composition. For instance, blends of resins can be used toadjust photospeed and thermal properties and to control dissolutionbehavior of a resist in a developer.

One suitable class of photoresists of the invention are “conventional”positive-acting resists that comprise a resin dye as discussed above, aphotoacid generator that serves as a dissolution rate inhibitor and aresin binder component such as a novolak or poly(vinylphenol) orpartially hydrogenated derivative thereof. Photoactivation of a coatinglayer of the resist results in conversion of the photoactive componentto an acidic material, rendering regions of the coating layer containingthis acidic photoproduct comparatively more soluble in an aqueousalkaline developer solution than regions that contain only the intact(non-activated) photoactive component. The photoactive componenttypically used in these positive resists are quinone diazides such as2,1,4-diazonaphthoquinone sulfonic acid esters and2,1,5-diazonaphthoquinone sulfonic acid esters.

In particularly preferred aspects, the invention provides chemicallyamplified positive-acting resist compositions that contain a resin dyeas discussed above. A number of such resist compositions have beendescribed, e.g., in U.S. Pat. Nos. 4,968,581; 4,883,740; 4,810,613;4,491,628 and 5,492,793, all of which are incorporated herein byreference for their teaching of making and using chemically amplifiedpositive-acting resists. Particularly preferred chemically amplifiedphotoresists of the invention comprise in admixture a photoacidgenerator and a resin binder that comprises a copolymer containing bothphenolic and non-phenolic units. For example, one preferred group ofsuch copolymers has acid labile groups substantially, essentially orcompletely only on non-phenolic units of the copolymer. One especiallypreferred copolymer binder has repeating units x and y of the followingformula:

wherein the hydroxyl group be present at either the ortho, meta or parapositions throughout the copolymer, and R′ is substituted orunsubstituted alkyl having 1 to about 18 carbon atoms, more typically 1to about 6 to 8 carbon atoms. Tert-butyl is a generally preferred R′group. An R′ group may be optionally substituted by e.g. one or morehalogen (particularly F, Cl or Br), C₁₋₈ alkoxy, C₂₋₈ alkenyl, etc. Thedepicted phenolic units of the polymer also may be optionallysubstituted by such groups. The units x and y may be regularlyalternating in the copolymer, or may be randomly interspersed throughthe polymer. Such copolymers can be readily formed. For example, forresins of the above formula, vinyl phenols and a substituted orunsubstituted alkyl acrylate such as t-butylacrylate and the like may becondensed under free radical conditions as known in the art. Thesubstituted ester moiety, i.e. R′—O—C(═O)—, moiety of the acrylate unitsserves as the acid labile groups of the resin and will undergo photoacidinduced cleavage upon exposure of a coating layer of a photoresistcontaining the resin. Preferably the copolymer will have a Mw of fromabout 8,000 to about 50,000, more preferably about 15,000 to about30,000 with a molecular weight distribution of about 3 or less, morepreferably a molecular weight distribution of about 2 or less.Non-phenolic resins, e.g. a copolymer of an alkyl acrylate such ast-butylacrylate or t-butylmethacrylate and a vinyl alicyclic such as avinyl norbornyl or vinyl cyclohexanol compound, also may be used as aresin binder in compositions of the invention. Such copolymers also maybe prepared by such free radical polymerization or other knownprocedures and suitably will have a Mw of from about 8,000 to about50,000, and a molecular weight distribution of about 3 or less.Additional preferred chemically-amplified positive resists are disclosedin U.S. Pat. No. 5,258,257 to Sinta et al.

Preferred negative-acting resist compositions of the invention comprisea resin dye as discussed above and a mixture of materials that willcure, crosslink or harden upon exposure to acid.

Particularly preferred negative-acting resist compositions comprise aresin dye of the invention, a resin binder such as a phenolic resin, acrosslinker component and a photoacid generator. Such compositions andthe use thereof have been disclosed in European Patent Applications0164248 and 0232972 and in U.S. Pat. No. 5,128,232 to Thackeray et al.Preferred phenolic resins for use as the resin binder component includenovolaks and poly(vinylphenol)s such as those discussed above. Preferredcrosslinkers include amine-based materials, including melamine,glycourils, benzoguanamine-based materials and urea-based materials.Melamine-formaldehyde resins are generally most preferred. Suchcrosslinkers are commercially available, e.g. the melamine resins soldby American Cyanamid under the trade names Cymel 300, 301 and 303.Glycouril resins are sold by American Cyanamid under trade names Cymel1170, 1171, 1172, Powderlink 1174, urea-based resins are sold under thetrade names of Beetle 60, 65 and 80, and benzoguanamine resins are soldunder the trade names Cymel 1123 and 1125.

Sulfonate compounds are generally preferred PAGs, particularly sulfonatesalts. Two specifically preferred agents are the following PAGS 1 and 2:

These sulfonate compound can be prepared as disclosed in Example 7 whichfollows, which details the synthesis of above PAG 1. Sulfonate PAG 2above can be prepared by the same procedures of Example 7 which follows,except approximately molar equivalents of t-butyl benzene and benzenewould be reacted together in the first step with acetic anhydride andKIO₃. Also preferred are the above two iodonium compounds with counteranions of trifluoromethylsulfonate (CF₃SO₃) and benzenesulfonate. Thesesulfonate PAGS are particularly preferred for use in thechemically-amplified positive photoresists of the invention.

Other suitable sulfonate PAGS including sulfonated esters andsulfonyloxy ketones. See J. of Photopolymer Science and Technology,4(3):337–340 (1991), for disclosure of suitable sulfonate PAGS,including benzoin tosylate, t-butylphenylα-(p-toluenesulfonyloxy)-acetate and t-butylα-(p-toluenesulfonyloxy)-acetate. Preferred sulfonate PAGs are alsodisclosed in U.S. Pat. No. 5,344,742 to Sinta et al.

Onium salts are also generally preferred acid generators of compositionsof the invention. Onium salts that weakly nucleophilic anions have beenfound to be particularly suitable. Examples of such anions are thehalogen complex anions of divalent to heptavalent metals or non-metals,for example, Sb, Sn, Fe, Bi, Al, Ga, In, Ti, Zr, Sc, D, Cr, Hf, and Cuas well as B, P, and As. Examples of suitable onium salts arediaryl-diazonium salts and onium salts of group Va and B, Ia and B and Iof the Periodic Table, for example, halonium salts, quaternary ammonium,phosphonium and arsonium salts, aromatic sulfonium salts and sulfoxoniumsalts or selenium salts. Examples of suitable preferred onium salts canbe found in U.S. Pat. Nos. 4,442,197; 4,603,101; and 4,624,912.

Other useful acid generators include the family of nitrobenzyl esters,and the s-triazine derivatives. Suitable s-triazine acid generators aredisclosed, for example, in U.S. Pat. No. 4,189,323.

Halogenated non-ionic, photoacid generating compounds are also suitablesuch as, for example, 1,1-bis[p-chlorophenyl]-2,2,2-trichloroethane(DDT); 1,1-bis[p-methoxyphenyl]-2,2,2-trichloroethane;1,2,5,6,9,10-hexabromocyclodecane; 1,10-dibromodecane;1,1-bis[p-chlorophenyl]-2,2-dichloroethane;4,4-dichloro-2-(trichloromethyl)benzhydrol (Kelthane);hexachlorodimethyl sulfone; 2-chloro-6-(trichloromethyl) pyridine;o,o-diethyl-o-(3,5,6-trichloro-2-pyridyl)phosphorothionate;1,2,3,4,5,6-hexachlorocyclohexane;N(1,1-bis[p-chlorophenyl]-2,2,2-trichloroethyl)acetamide;tris[2,3-dibromopropyl]isocyanurate;2,2-bis[p-chlorophenyl]-1,1-dichloroethylene;tris[trichloromethyl]s-triazine; and their isomers, analogs, homologs,and residual compounds. Suitable photoacid generators are also disclosedin European Patent Application Nos. 0164248 and 0232972. Acid generatorsthat are particularly preferred for deep U.V. exposure include1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT);1,1-bis(p-methoxyphenol)-2,2,2-trichloroethane;1,1-bis(chlorophenyl)-2,2,2 trichloroethanol;tris(1,2,3-methanesulfonyl)benzene; and tris(trichloromethyl)triazine.

As discussed above, the invention also provides photoresist compositionsthat include a photobase generator compound, particularly negativebase-hardening compositions that contain a dye material of theinvention, a resin binder such as the above-discussed phenolic resins, acrosslinker and a photobase generator compound that undergoes abase-promoted crosslinking reaction upon exposure to activatingradiation. Suitable photobase generator compounds and the use ofbase-hardening composition are disclosed in U.S. Pat. No. 5,262,280 toKnudsen et al. Amine-based crosslinkers such as the above-discussedmelamine resins are suitable for base-hardening compositions.

Photoresists of the invention also may contain other materials. Apreferred optional additive is an added base, particularlytetrabutylammonium hydroxide (TBAH), or lactate salt of TBAH (seeExample 7 which follows), which can enhance resolution of a developedresist relief image. The added base is suitably used in relatively smallamounts, e.g. about 1 to 20 percent by weight relative to thephotoactive component.

Other optional additives include anti-striation agents, plasticizers,speed enhancers, etc. Dye compounds in addition to the above-discussedresin materials also may be employed if desired. Such optional additivestypically will be present in minor concentration in a photoresistcomposition except for fillers and additional dyes which may be presentin relatively large concentrations such as, e.g., in amounts of from 5to 30 percent by weight of the total weight of a resist's drycomponents.

The compositions of the invention can be readily prepared by thoseskilled in the art. For example, a photoresist composition of theinvention can be prepared by dissolving the components of thephotoresist in a suitable solvent such as, for example, ethyl lactate, aglycol ether such as 2-methoxyethyl ether (diglyme), ethylene glycolmonomethyl ether, ethylene glycol monomethyl ether, propylene glycolmonomethyl ether; a Cellosolve ester or a ketone such as methyl ethylketone. Typically, the solids content of the composition varies betweenabout 5 and 35 percent by weight of the total weight of the photoresistcomposition. The resin binder and PAG components should be present inamounts sufficient to provide a film coating layer and formation of goodquality latent and relief images. See the examples which follow forexemplary preferred amounts of resist components.

The compositions of the invention are used in accordance with generallyknown procedures. The liquid coating compositions of the invention areapplied to a substrate such as by spinning, dipping, roller coating orother conventional coating technique. When spin coating, the solidscontent of the coating solution can be adjusted to provide a desiredfilm thickness based upon the specific spinning equipment utilized, theviscosity of the solution, the speed of the spinner and the amount oftime allowed for spinning.

The resist compositions of the invention are suitably applied tosubstrates conventionally used in processes involving coating withphotoresists. For example, the composition may be applied over siliconor silicon dioxide wafers for the production of microprocessors andother integrated circuit components. Aluminum-aluminum oxide, galliumarsenide, ceramic, quartz or copper substrates also may be employed.Substrates used for liquid crystal display and other flat panel displayapplications are also suitably employed, e.g. glass substrates, indiumtin oxide coated substrates and the like.

Following coating of the photoresist onto a surface, it is dried byheating to remove the solvent until preferably the photoresist coatingis tack free. Thereafter, it is imaged through a mask in conventionalmanner. The exposure is sufficient to effectively activate thephotoactive component of the photoresist system to produce a patternedimage in the resist coating layer and, more specifically, the exposureenergy typically ranges from about 10 to 300 mJ/cm², dependent upon theexposure tool and the components of the photoresist composition.

Coating layers of the resist compositions of the invention arepreferably photoactivated by an exposure wavelength in the deep U.V.range i.e., 350 nm or less, more typically in the range of about 300 nmor less, typically about 150 to 300 or 350 nm. A particularly preferredexposure wavelength is about 248 nm.

Following exposure, the film layer of the composition is preferablybaked at temperatures ranging from about 50° C. to about 160° C. tocreate or enhance solubility differences between exposed and unexposedregions of a coating layer. For example, negative photoresists typicallyrequire post-exposure heating to induce an acid-promoted orbase-promoted crosslinking reaction, and many chemically amplifiedpositive-acting resists require post-exposure heating to induce anacid-promoted deprotection reaction.

After any such post-exposure bake, the film is developed, preferablyusing an aqueous-based developer such as an inorganic alkali exemplifiedby sodium hydroxide, potassium hydroxide, sodium carbonate, sodiumbicarbonate, sodium silicate, sodium metasilicate; quaternary ammoniumhydroxide solutions such as a tetra-alkyl ammonium hydroxide solution;various amine solutions such as ethyl amine, n-propyl amine, diethylamine, di-n-propyl amine, triethyl amine, or methyldiethyl amine;alcohol amines such as diethanol amine or triethanol amine; cyclicamines such as pyrrole, pyridine, etc. In general, development is inaccordance with art recognized procedures.

Following development of the photoresist coating over the substrate, thedeveloped substrate may be selectively processed on those areas bared ofresist, for example by chemically etching or plating substrate areasbared of resist in accordance with procedures known in the art. For themanufacture of microelectronic substrates, e.g., the manufacture ofsilicon dioxide wafers, suitable etchants include a plasma gas etch(e.g. an oxygen plasma etch) and a hydrofluoric acid etching solution.The compositions of the invention are highly resistant to such etchantsthereby enabling manufacture of highly resolved features, includinglines with submicron widths. After such processing, resist may beremoved from the processed substrate using known stripping procedures.

All documents mentioned herein are incorporated herein in their entiretyby reference. The following non-limiting examples are illustrative ofthe invention.

General Comments

In following examples, the methylanthracene methacrylate-hydroxyethylmethacrylate (ANTMA-HEMA) copolymer resin used as a dye in the resistformulations was the material of Formula III produced according toExample 1 which follows, with an Mn, Mw and percent anthracene units andother properties as disclosed in that example. The resin binder materialused in the following examples was a copolymer of vinyl phenol andt-butylacrylate having a Mw of about 20,000 and available under thetradename of Maruzen CTBA 161 from Maruzen Oil Company of Tokyo, Japan.The Silwet™ L-7604 leveling agent used in the examples is commerciallyavailable from Union Carbide.

EXAMPLE 1 Preparation of Preferred Dye Resins

1. Preparation of Monomers with Chromophores.

A. Preparation of Chloroxine Methacrylate.

A 500 ml round bottom flask equipped with magnetic stirrer and nitrogeninlet was charged with 5.0 g (0.0234 mol) 5.7dichloro-8-hydroxyquinoline (chloroxine), 2.01 (0.0234 mol)methacrylicacid, 500 ml methylene chloride, 1.43 g (0.5 eq.),4-dimethylamino-pyridine (DMAP) and 6.72 g 1-(3-dimethylaminopropyl)-3-ethylcarbodimide (EDCI). The reaction mixture was stirredunder a blanket of nitrogen for 12 hours at 25° C. The product waspurified by column chromatography (methylene chloride) to give a paleyellow solid (yield 67%).

B. Preparation of Methylanthracene Methacrylate

Methylanthracene methacrylate (CH₃C(═CH₂)CO₂CH₂-9-anthracene) wasprepared as disclosed in Macromolecules, 17(2):235 (1984).

2. Preparation of Resins.

Methylanthracene methacrylate (ANTMA)/hydroxyethyl methacrylate (HEMA)copolymer (Formula III below) was prepared as follows.

A 300 ml 3-neck round bottom flask equipped with magnetic stirrer,condenser, nitrogen and vacuum inlet was charged with 16.0 g (0.1229mol) HEMA (purified by distillation), 8.49 g (0.0307mol)methylanthracene methacrylate, 0.2449 g (1 wt. %) AIBN and 180 mlTHF. The reaction flask was quenched in liquid nitrogen while beingpurged with nitrogen. When the contents of the reaction flask werefrozen, the flask was evacuated, then purged with nitrogen (3 times).The reaction mixture was stirred under reflux for 18 hours. The paleyellow polymer was precipitated into 3000 ml ether, filtered, then driedat 50° C. under vacuum (yield 86%) to provide the ANTMA/HEMA copolymerhaving 81 mole percent of —CH₂C(CH₃)(CO₂CH₂CH₂OH)— units and 19 molepercent of —CH₂C(CH₃)(CO₂CH₂-9-anthracene) units, a Mn of 2295, Mw of19150 and a Tg of 101° C. This ANTMA/HEMA dye resin had the structure ofthe following Formula III, with x equal to about 81 percent and y equalto about 19 percent:

Additional ANTMA/HEMA copolymers and HEMA/chloroxine methacrylatecopolymers were prepared by similar procedures, with the substitution ofchloroxine methacrylate for methylanthracene methacrylate in the case ofpreparation of HEMA/chloroxine methacrylate copolymers.

EXAMPLE 2

A solution consisting of 10.664 g of ANTMA/HEMA dye solution (5 wt % ofANTMA/HEMA resin of Formula III in ethyl lactate), 2.664 gpolyhydroxystyrene-t-butylacrylate copolymer solids, 0.126 g Silwet™L-7604 Surfactant solution (10% solids in Ethyl Lactate) and 6.525 gadditional ethyl lactate was prepared. The solution was filtered througha 0.2 μm pore-size PTFE membrane filter.

Solutions of other dye materials were also formulated, using the samedye concentration as the ANTMA/HEMA copolymer. Those dyes are specifiedin Table I below. A sample with no dye material was also evaluated.

Quartz and silicon wafers were coated with the dyed polymer solutionsfor determining optical properties. Wafers were soft baked for 60seconds at 100° C., vacuum hot plate, on a GCA MicroTrack coat and bakesystem. Silicon wafers were used for thickness and cauchy coefficientdeterminations. Absorbance spectra from 200 nm to 500 nm were taken on aCary 13 UV-VIS Spectrophotometer; absorbance values (ABS) for 248 nm areset forth in Table I below. Quartz wafers were subsequently baked for 60seconds at 125° C. and 150° C. (spectral curves run following eachbake).

TABLE I % Dye Soft Bake ABS/1.0 μm % Change Dye Loading Temp, ° C. @ 248nm in ABS 5-Nitrobenzotriazole 20% 100 1.6659 — 125 1.6205 2.7% 1501.2124 27.2% 4-Phenylazodiphenyl- 20% 100 0.7659 — amine 125 0.764480.1% 150 0.7000 8.6% Aminoanthracene 20% 100 2.9596 — 125 2.7907 5.7%150 1.5438 47.8% t-Butylanthraquinone 20% 100 1.8004 — 125 1.7882 0.7%150 1.1664 35.2% ANTMA/HEMA 20% 100 2.0291 — dye resin 125 2.0603 −1.5%(prepared per Ex. 1) 150 2.0849 −2.7% No Dye Not 100 0.1267 — applic.125 0.1379 −8.8% 150 0.1222 −3.6%

EXAMPLE 3

A photoresist composition (Resist 1) consisting of 6.083 gpolyhydroxystyrene-t-butylacrylate copolymer solids, 2.432 gdi-t-butylphenyliodonium camphorsulfonate photoacid generator solution(10 wt % solids in ethyl lactate), 0.136 g of a tetrabutyl ammoniumhydroxide lactate solution (10 wt % solids in ethyl lactate), 0.181 gANTMA/HEMA dye solution (34 wt % solids in 37.5 vol % Anisole:62.5 vol %propylene glycol monomethyl ether acetate), 0.322 g Silwet™ L-7604Surfactant solution (10 wt % solids in ethyl lactate) and 30.850 gadditional ethyl lactate was prepared.

Two additional photoresists (Resist 2 and Resist 3) were formulated inthe samme manner as for Resist 1 and described about, except the amountof ANTMA/HEMA dye solution was varied to adjust the optical density ofthe photoresist film: Resist 2 contained 0.524 g of the ANTMA/HEMA dyesolution and Resist 3 contained 0.864 g of the ANTMA/HEMA dye solution.Resists 1–3 thus contained 1, 3% and 5% dye solids (wt.)/polymer solids(wt.), respectively.

Silicon wafers were primed with HMDS and coated with each of Resists to0.86 μm film thickness. A Prometrix SM300 film thickness measurementtool was used for film thickness measurements. Quartz wafers were alsocoated with the photoresists for determining optical properties, withrecorded absorbance values specified in Table II below. Wafers were softbaked for 60 seconds at 130° C., vacuum hot plate, on a GCA MicroTrackcoat and bake system. Coated wafers were then exposed on a GCA XLS 7800excimer laser stepper fitted with a reticle consisting of blank quartzor dense line/space pairs and isolated lines. Exposed wafer were thenpost-exposure baked for 90 seconds at 140° C. and developed with a 60second single spray puddle on a GCA Microtrack system using ShipleyMicroposit CD-26 0.26N tetramethylammonium hydroxide developer.

Soft baked, resist coated, wafers were exposed in 0.2 mJ/cm² incrementsfrom 0.2 to 20.0 mJ/cm² using the blank quartz reticle. Following thepost-exposure bake, resists were developed. Required exposure energieswere determined (see Table III below) and focus-exposure arrays were runusing the dense line/space pairs and isolated line reticle.

TABLE II Resist No. Absorbance Units/1.0 μm Resist 1 0.2780 Resist 20.36390 Resist 3 0.60220

TABLE III Resist No. Eo Dose Esize Dose L/S Resolution Resist 1 3.4mJ/cm² 11.0 mJ/cm² 0.200 μm Resist 2 4.2 mJ/cm² 14.0 mJ/cm² 0.200 μmResist 3 5.2 mJ/cm² 18.5 mJ/cm² 0.200 μm

EXAMPLE 4

Two photoresists were formulated, one containing the ANTMA/HEMA dyeresin of Example 1 above and one without the dye component. The dyedresist consisted of 5.860 g polyhydroxystyrene-t-butylacrylate copolymersolids, 2.345 g di-t-butylphenyl iodonium camphorsulfonate photoacidgenerator solution (10% solids in ethyl lactate), 0.131 g of atetrabutylammonium hydroxide lactate solution (10% solids in ethyllactate), 0.864 g ANTMA/HEMA dye solution (34 wt % solids in 37.5 vol %Anisole:62.5 vol % propylene glycol monomethyl ether acetate), 0.322 gSilwet™ L-7604 surfactant solution (10 wt % solids in ethyl lactate) and30.491 g additional ethyl lactate. The non-dyed resist contained 13.249g polyhydroxystyrene-t-butylacrylate copolymer solids, 5.374 gdi-t-butylphenyliodonium camphorsulfonate photoacid generator solution(10 wt % solids in ethyl lactate), 0.333 g of a tetrabutylammoniumhydroxide lactate solution (10 wt % solids in ethyl lactate) and 80.164g additional ethyl lactate.

Silicon wafers were primed with HMDS and coated with the resists to castfilms from 6600 Å to 7800 Å film thickness. A Prometrix SM300 filmthickness measurement tool was used for film thickness measurements.Wafers were soft baked for 60 seconds at 130° C., vacuum hot plate, on aGCA MicroTrack coat and bake system. Coated wafers were then exposed ona GCA XLS 7800 excimer laser stepper fitted with a reticle consisting ofblank quartz. Exposed wafers were then post-exposure baked for 90seconds at 140° C. and developed with a 60 second single spray puddle ona GCA Microtrack system using Shipley Microposit CD-26 0.26Ntetramethylammonium hydroxide developer.

Required exposure energy to clear the resist (Eo mJ/cm²), versus filmthickness was determined. The resist containing the ANTMA/HEMA resin dyereduced the exposure dose swing by 50%; specifically, the exposure doseswing was approximately 44% for the non-dyed resist and approximately21% for the resist with the ANTMA/HEMA resin dye.

EXAMPLE 5

Four resists were formulated, three containing the ANTMA/HEMA resin dyeat various dye loadings as specified below (to modify the resist filmoptical density) and one without the dye component. The resists wereformulated as follows:

Non-Dyed Low Dye Medium High Component 0.24 AU/μm 0.33 AU/μm 0.45 AU/μm0.59 AU/μm Resin binder 40.347 g 40.347 g 40.347 g 40.347 g PAG 1.614 g1.614 g 1.614 g 1.614 g Stabilizer 0.090 g 0.090 g 0.090 g 0.090 g Resindye 0 0.319 g 0.759 g 1.295 g Surfactant 0.210 g 0.210 g 0.210 g 0.210 gEthyl lactate 207.740 g 208.21 g 208.87 g 209.683 g Resin binder:polyhydroxystyrene-t-butylacrylate copolymer PAG:Di-t-butylphenyliodonium camphorsulfonate photoacid generator Resin dye:ANTMA/HEMA copolymer Surfactant: Silwet ™ L-7604 Stabilizer: TBAHlactate salt

Silicon wafers were primed with HMDS and coated with the resists to castfilms from 7600 Å (Emin. dose) and 7235 Å (Emax. dose) film thickness. APrometrix SM300 film thickness measurement tool was used for filmthickness measurements. Wafers were soft baked for 60 seconds at 130°C., vacuum hot plate, on a GCA MicroTrack coat and bake system. Coatedwafers were then exposed on a GCA XLS 7800 excimer laser stepper fittedwith a reticle consisting of blank quartz or dense line/space pairs andisolated lines. Exposed wafers were then post-exposure baked for 90seconds at 140° C. and developed with a 60 second single spray puddle ona GCA Microtrack system using Shipley Microposit CD-26 0.26 Ntetramethylammonium hydroxide developer.

As dyed loading increased, standing waves were significantly reduced asshown by scanning electron micrograph (SEM) analysis of the developedresist relief images.

Resolution and masking linearity capabilities of the medium dyed resistwere better than the non-dyed resist as shown by the SEMs.

Further, both depth-of-focus and exposure latitudes improved with thedyed photo resist relative to the non-dyed resist.

EXAMPLE 6

Reproducibility of the properties ANTMA/HEMA resin dye was studied using3 different synthesis lots of the ANTMA/HEMA resin dye; those lots weredesignated as follows: Batch 1; Batch 2; and Batch 3.

Three photoresists compositions (Resists 1–3) were prepared. Resist 1contained 0.142 g of the dye of Batch 1, Resist 2 contained 0.142 g ofthe dye of Batch 2 and Resist 3 contained 0.142 g of the dye of Batch 3.Each of Resists 1–3 also contained 37.700 gpolyhydroxystyrene-t-butylacrylate copolymer solution (20% solids inethyl lactate), 3.016 g di-t-butylphenyliodonium camphorsulfonatephotoacid generator solution (10% solids in ethyl lactate), 0.167 g of astabilizing additive solution (10% solids in ethyl lactate) and 8.575 gadditional ethyl lactate.

Silicon wafers were primed with HMDS and coated with the resists to0.765 μm film thickness. A Prometrix SM300 film thickness measurementtool was used to measure film thickness. Wafers were soft baked for 60seconds at 130° C., vacuum hot plate, on a GCA MicroTrack coat and bakesystem. Coated wafers were then exposed on a GCA XLS 7800 excimer laserstepper fitted with a reticle consisting of blank quartz or denseline/space pairs and isolated lines. Exposed wafer were thenpost-exposure baked for 90 seconds at 140° C. and developed with a 20second/25 second double spray puddle on a GCA Microtrack system usingShipley Microposit CD-26 0.26N tetramethylammonium hydroxide developer.

Soft baked, resist coated, wafers were exposed in 0.2 mJ/cm² incrementsfrom 0.2 to 20.0 mJ/cm² using the blank quartz reticle. Following thepost-exposure bake, resists were developed. Required exposure energieswere determined and a focus-exposure arrays were run using the denseline/space pairs and isolated line reticle. Results are set forth inTable IV below.

TABLE IV Resist Eo Dose Esize Dose L/S Resolution Resist 1 3.4 mJ/cm²10.2 mJ/cm² 0.220 μm Resist 2 3.2 mJ/cm² 11.2 mJ/cm² 0.220 μm Resist 33.2 mJ/cm² 11.2 mJ/cm² 0.200 μm

EXAMPLE 7

The PAG 1 above, (di-(4-t-butylphenyl)iodonium(+/−)-10-camphorsulfonate, can be prepared as follows. A 2 L 3-neckround bottom flask was charged with potassium iodate (214.00 g, 1.00mol), t-butylbenzene (268.44 g, 2.00 mol) and acetic anhydride (408.36g, 4.00 mol). The flask was fitted with an efficient overhead paddlestirrer, a thermometer and a pressure equalizing dropping funnel fittedwith a N₂ bubbler. The reaction mixture was cooled to 10° C. in aice-water bath and concentrated sulfuric acid (215.78 g, 2.20 mol) addeddropwise via the addition funnel. The addition was carried out at such arate as to maintain the reaction temperature around 25° C. and required2 hours. As the addition proceeded the starting white suspension becameorange-yellow in color. Once the addition was over, the reaction mixturewas stirred at room temperature (20° C.) for an additional 22 hours. Thereaction mixture was cooled to 5–10° C. and water (600 ml) was addeddropwise over a period of 30 minutes, maintaining the temperature below30° C. (Note the first @75 ml should be added at a particularly slowrate as to control the initial exotherm, thereafter the rest of thewater may be added at a faster rate). This cloudy mixture was washedwith hexane (3×100 ml) (to remove unreacted t-butylbenzene and some4-t-butyliodobenzene byproduct) in a 2 L separating funnel and theaqueous solution of diaryliodonium hydrogensulfate transferred to a 3 Lreaction vessel. The solution was cooled to 5–10° C.,(+/−)-10-camphorsulfonic acid (232.30 g, 1.00 mol) was added in oneportion with stirring and the solution was then neutralized withammonium hydroxide (620 ml, 9.20 mol). The amount of base used was thetheoretical amount required to neutralize all acidic species in the pot,assuming quantitative reaction. The addition of the base is carried outat such a rate as to keep the temperature below 25° C. and takes about 1hour. As the addition nears completion and the pH of the reactionmixture approaches 7, the crude diaryliodonium camphorsulfonateprecipitated as a tan solid. This suspension was allowed to stir at roomtemperature for 3 hours and the material isolated as follows: The tansolid was collected by suction filtration and while still moist taken upin dichloromethane (1 L) and washed with dilute ammonium hydroxide (2.5wt %, 5 ml 14.8 N NH₄OH+195 ml H₂O) until the washings are in the pH 7–8range (1×200 ml) and then water (2×200 ml) to restore the pH to around7. After drying (MgSO₄), the dichloromethane was removed under reducedpressure and the residue further dried in vacuo at 50° C. for 16 hoursto give the crude product as a tan solid (390.56 g). The resulting tansolid was then purified by recrystallization in the following manner.The tan solid was dissolved in the minimum amount of refluxingisopropanol (@ 375 g PAG in @ 1150 ml IPA) in a 2 L round bottom flaskto give a homogeneous dark red solution. The hot solution wastransferred to a 2 L conical flask and allowed to cool. While thissolution was still warm, hexane (500 ml) was added and crystals formedsoon after. The crystallizing mixture was allowed to cool to roomtemperature and stored for 4 hours. The crystallizing solution wascooled to @ 5° C. in an ice-water bath for 1.5 hours and then the solidwas collected by suction filtration and washed until white with verycold isopropanol-hexane (1:3, 2×200 ml, prepared by cooling the solventmixture in a dry ice-acetone bath before use). The white solid was driedunder aspirator vacuum for 1 hour until the PAG(di-(4-t-butylphenyl)iodonium (+/−)-10-camphorsulfonate) was isolated asa free flowing white powder. At this stage about 285 g of PAG isobtained. A second recrystallization can be performed in a similarmanner.

A lactate salt of TBAH (tetra-n-butylammoniumd/1-lactate salt;[(CH₃CH₂CH₂CH₂)₄NO(CO)CH(OH)CH₃]) can be prepared as follows. To asolution of tetra-n-butylammonium bromide (16.12 g, 50.0 mmol) in water(50 ml) was added a gray colored suspension of silver lactate (9.85 g,50.0 mmol) in water (100 ml). As the addition proceeded a grayish whitesolid, presumably silver bromide, precipitated from solution. Theresulting suspension was stirred at room temperature for 15 hours, thesolid was filtered off and washed with water (3×50 ml). The combinedfiltrate and washings were concentrated under reduced pressure and theresidual oil dried in vacuo at 50° C. for 24 hours to give the titlecompound as a colorless oil (16.62 g, 99%). Upon standing at roomtemperature, this oil later formed a waxy semi-solid.

The foregoing description of the invention is merely illustrativethereof, and it is understood that variations and modifications thereofcan be made without departing from the spirit or scope of the inventionas set forth in the following claims.

1. A photoresist composition that comprises a resin binder, a photoacidgenerator compound and a dye that comprises a structure of the followingformula:

each R² is independently substituted or unsubstituted alkyl; W′ is abond or substituted or unsubstituted alkylene; G is a carbon, nitrogen,oxygen or sulfur; each R³ may be independently halogen; substituted orunsubstituted alkyl; substituted or unsubstituted alkoxy; substituted orunsubstituted alkenyl; substituted or unsubstituted alkynyl; substitutedor unsubstituted alkylthio; cyano; nitro; amino and hydroxy; m is aninteger of from 0 to 7; x′ and y′ are mole fractions of the respectiveunits; and each Z is a bridge group between polymer units.
 2. Thephotoresist of claim 1 wherein the polymer has a weight averagemolecular weight of at least about 5,000.
 3. The photoresist of claim 1wherein the photoresist is a chemically-amplified positive-actingresist.
 4. The method of claim 1 wherein the photoresist is anegative-acting resist.